Summary Regular aerobic exercise with sufficient intensity can improve overall health, however daily energy expenditure is low in those with SCI, especially in those with high level lesions. We have developed Functional Electrical Stimulation Row Training (FESRT) that couples volitional arm and electrically controlled leg exercise, increasing the active muscle and resulting in benefits of large muscle mass exercise. Despite the potential for enhancing aerobic capacity, those with high level lesions (C4 to T2) have a remaining obstacle to attaining higher work capacities they have the greatest pulmonary muscle denervation and our preliminary work suggests this limits the aerobic capacity that can be achieved with FESRT. External ventilatory support could improve the ability to exercise train and hence enhance the adaptations to chronic exercise in high level SCI. Non invasive ventilation (NIV) during exercise training has been shown to improve gains in exercise capacity in those with similarly restrictive breathing. Therefore, we hypothesize that the use of NIV during FESRT will reduce ventilatory limits to exercise, leading to increased aerobic capacity in high level SCI. Our aims are to determine the magnitude of improvement in aerobic capacity and its relationship to increases in maximal cardiac output and arterio venous oxygen difference after 4 months of FESRT+NIV compared to FESRT+shamNIV. We have access to a large (N>70) and unique population of individuals with SCI who have been enrolled in FESRT for at least 6 months. Roughly half have SCI between C4 and T2. 30 individuals with high level SCI who have FES row trained for at least 6 months will be randomized to (continued) FESRT for 4 months with either NIV or sham NIV. Before and after training, we will assess maximal aerobic capacity, ventilation, cardiac output, and arterio venous oxygen difference. Based on our current data, we hypothesize that only those randomized to NIV will experience further increases in aerobic capacity and that these increases will relate to increased cardiac output and arterio venous oxygen difference. This Exploratory/Developmental Research project will determine feasibility and effectiveness of this approach to exercise and will lay the groundwork for a larger, controlled trial.